1. Field of Invention
The embodiments of the invention relate in general to Internet protocol (IP) multicast networks. More specifically, the embodiments of the invention relate to methods and systems for adaptively computing an encoding rate of a multimedia stream in an IP multicast network.
2. Description of the Background Art
Multimedia data, such as audio and video, has become a common and increasingly popular form of content transmitted across modern communication networks. Typically, while accessing multimedia data across a network, a user had to wait for the entire file to be downloaded before he could use the information. Streaming technology allows the multimedia data to be delivered to the user as a continuous flow with minimal delay, before playback can begin. Streaming is a server/client technology that allows live or pre-recorded data to be broadcast in real time.
There are two key streaming delivery techniques for multimedia data—unicast and multicast. Unicast refers to a networking technique, in which a single data stream is directed from a server to a single network device, in response to a request from the network device. This is the traditional way to send information to a single recipient, or to a few recipients. In this one-to-one relationship, a single message is transmitted to a recipient's unique address. When sending the same message to multiple recipients via unicast data streams, a separate copy of the message is transmitted to each recipient's individual address. Unicast data streaming is adequate for many on-demand multimedia systems, and for delivering multimedia streams to a limited number of recipients. However, as the number of network devices making requests to the server increases, a lot of network bandwidth is wasted.
IP multicast is a bandwidth-conserving technology that reduces traffic by simultaneously delivering a single data stream to multiple recipients. IP multicast networking operates by transmitting a single data stream from a server to a group of receivers connected to the network. Multicast routers control the flow of the single data stream along the network. Multicast is based on the concept of a group, which includes receivers who express an interest in receiving a particular data stream. Since, the server needs to send only a single stream of data, the IP multicast preserves the network bandwidth. Replication of a single stream of data is done in the IP multicast networks if there are more than one outgoing interfaces (OIFs), and the receivers are present on the OIFs. An IP multicast is applied in areas such as videoconferencing, corporate communications, distance learning, and distribution of software, stock quotes and news.
In a conventional IP multicast, a multimedia stream is typically encoded at a source at a predetermined transmission rate, with the assumption that the network would always have sufficient bandwidth to support the rate at which the multimedia stream is encoded. However, if the multimedia stream is encoded at a transmission rate that is greater than the available transmission rate, the receiver may be unable to receive the information at the data rate necessary to support the underlying application, thereby causing the application to be disrupted or give a degrading performance. The conventional IP multicast networks lack an efficient mechanism to change the encoding rate of the multimedia streams according to a user-defined priority. Also, the conventional IP multicast networks lack an efficient mechanism to compute the encoding rate of the more popular multimedia streams in a way that ensures better delivery of the more popular multimedia streams over the less popular multimedia streams. As a result, there may not be efficient bandwidth utilization in the conventional IP multicast networks.